Cobalt Cerium Oxide Research Articles

Regulation of oxygen vacancies in cobalt-cerium oxide catalyst for boosting decontamination of VOCs by catalytic oxidation

Herein, we developed a series of self-assembled cobalt-cerium oxides (CoCe-x) with the regulated oxygen vacancies, to enhance the decontamination of air pollution with low-temperature catalytic oxidation, in which the typical volatile organic pollutant (VOCs), toluene, acted as the target. The oxygen vacancies in catalyst was tuned by the efficient incorporation of Co atoms into the lattice structure of ceria, and therefore improved the migration of oxygen species, the formation of surface adsorbed oxygen with high activity, as well as the redox recycles of Co3+/Co2+ and Ce4+/Ce3+. Due to the abundant oxygen vacancies, the CoCe-5 (Co loading of 5 wt%) catalyst exhibited the significantly enhanced performance in the low-temperature catalytic oxidation of toluene, on which the conversion temperature of toluene (T90) shifted to 192 °C, reduced by 23% compared with the ceria. From in situ DRIFT results, the surface adsorbed oxygen and lattice oxygen with high mobility played key roles in the excellent performance of CoCe-5 catalyst, which promoted the adsorption, activation and oxidation of toluene significantly, especially accelerating the rate-determining step of toluene oxidation, the breakage of aromatic ring.

Bimetallic MOF-Derived Synthesis of Cobalt-Cerium Oxide Supported Phosphotungstic Acid Composites for the Oleic Acid Esterification

The impregnation of phosphotungstic acid (HPW) with porous cobalt-cerium oxide (HPW@CoCeO) has been prepared by pyrolysis of CoCe-MOF and used for the production of methyl oleate from oleic acid and methanol. FTIR, XRD, SEM, TEM, N2 adsorption/desorption, and NH3-TPD were characterized for the prepared composites. Simultaneously, the effects of reaction time, substrate molar ratio, temperature, and catalyst loading on catalytic activity were highlighted, and the conversion of 67.2% was reached after 4 h at 60°C. Importantly, HPW@CoCeO was reusabe and reused more than eight times, and the oleic acid conversion could be maintained at 61.8% without significant activity loss. Thus, the HPW@CoCeO composite could be used as acid catalysts for sustainable energy production.

Effect of Small Molecular Organic Acids on the Structure and Catalytic Performance of Sol–Gel Prepared Cobalt Cerium Oxides towards Toluene Combustion

Cobalt cerium oxide catalysts with small molecular organic acids (SOAs) as chelating agents were prepared via the sol–gel method and investigated for the complete oxidation of toluene. Four kinds of natural SOAs, i.e. malic acid (MA), citric acid (CA), glycolic acid (GA), and tartaric acid (TA), were selected. The effect of organic acids on the composition, structure, morphology and catalytic performance of metal oxides is discussed in details. The cobalt cerium oxides catalysts were characterized by various techniques, including TG–DSC, XRD, SEM–EDS, N2–adsorption and desorption, XPS, and H2–TPR analyses. The results show that the nature of organic acids influenced the hydrolysis, condensation and calcination processes, as well as strongly affected the textural and physicochemical properties of the metal oxides synthesized. The best catalytic activity was obtained with the CoCe–MA catalyst, and the toluene conversion reached 90% at 242 °C. This outstanding catalytic activity could be related to its textural, redox properties and unique surface compositions and oxidation states. In addition, the CoCe–MA catalyst also showed excellent stability in long–time activity test.

The use of CeO2-Co3O4oxides as a catalyst for the reduction of N2O emission

The morphological characterization of a series of cobalt-cerium oxide composites prepared by the deposition of CeO2 onto Co3 O4 powder with a molar ratio of cerium oxide to Co3O4 in the range of 0 to 1 was performed. The powders were also impregnated with a solution of K2 CO3 to obtain the theoretical content of potassium atoms 2at·nm−2 . To investigate the effect of adding specific amount of CeO2 on the catalytic activity, the X-ray diffraction, SEM-EDX, laser particle size distribution and BET surface area measurements were used. The catalysts were tested through the low-temperature decomposition of nitrous oxide in the temperature range of 50°C to 700°C. The addition of CeO2 and K always moved the temperature of a complete N2O conversion towards lower temperatures (480°C-540°C to 340°C-420°C). The best catalytic properties were shown by the samples in which the ratio of cerium oxide to cobalt oxide ranged from 0.4 to 0.7.

Catalytic oxidation of NO over Mn–Co–Ce–Ox catalysts: effect of reaction conditions

Manganese–cobalt–cerium oxide (Mn–Co–Ce–Ox) catalysts were synthesized by the co-precipitation method and tested for activity in low-temperature catalytic oxidation of NO in the presence of excess O2. With the best Mn–Co–Ce mixed-oxide catalyst, approximately 80 % NO conversion was achieved at 150 °C and a space velocity of 35,000 h−1. The effect of reaction conditions (reaction temperature, volume fractions of NO and O2, gas hourly space velocity (GHSV), and catalyst stability) was investigated. The optimum reaction temperature was 150 °C. Increasing the O2 content above 3 % results in almost no improvement of NO oxidation. This catalyst enables highly effective removal of NO within a wide range of GHSV. Furthermore, the stability of the Me–Co–Ce–Ox catalyst was excellent; no noticeable decrease of NO conversion was observed in 40 h.

Efficient cobalt–manganese oxide catalyst deposited on modified AC with unprecedented catalytic performance in CO preferential oxidation

In comparison to the supported cobalt–cerium oxide catalyst on AC, we first fabricated a novel and highly-efficient cobalt–manganese non-precious metal catalyst deposited on modified AC with unprecedented catalytic activity and extremely wide temperature-operation window for CO complete removal from an H 2 -rich stream, which resulted from the strong interaction of finely dispersed cobalt–manganese primarily confirmed by various characterization results. The high catalytic activity and extremely broad temperature-operation window allow the developed catalyst to possess a fascinating perspective for large-scale application in industry. ► A novel and highly-efficient Co Mn/AC–DP CO PROX catalyst was first fabricated. ► It shows much high activity and extremely wide temp-window for 100% CO removal. ► High activity is ascribed to dispersity, crystallinity and interaction of Co Mn. ► The physiochemical properties are strongly affected by diverse supporting methods. ► Unprecedented properties allow it to possess fascinating perspective in industry.

Structural characteristics of supported cobalt–cerium oxide catalysts used in Fischer–Tropsch synthesis

Cobalt cerium oxide catalysts were prepared using co-precipitation procedure and used for Fischer–Tropsch synthesis. The effect of a range of preparation variables on the composition, structure and morphology of cobalt cerium oxide catalysts before and after CO hydrogenation has been investigated. Characterization of different precursors and calcined catalysts was carried out using XRD, SEM, TPR, BET surface area measurements and thermal analysis methods such as TGA and DSC. It was found that all different preparation variables influenced the structure and morphology of the catalyst precursors and calcined catalysts.

Low-temperature catalytic oxidation of NO over Mn–Co–Ce–Ox catalyst

A series of manganese–cobalt–cerium oxide (Mn–Co–Ce–Ox) catalysts were prepared by co-precipitation method and tested for low temperature (<200°C) catalytic oxidation of NO in the presence of O2. The experimental results showed that the best catalyst yielded about 80% NO conversion at 150°C with a space velocity of 35,000h−1. As the cerium content was increased from 0% to 20% (mass%), NO conversion increased significantly, while decreased at higher cerium contents (30–40%). As comparison, single oxides were also investigated, and their activities were slower than those of Mn–Co–Ce–Ox catalyst. The effect of O2 (0–11%) was evaluated, and it is almost constant when the concentration of O2 was above 3%. The activity was suppressed with the coexisting of H2O and SO2 due to the generation of nitrates and sulfates, and the activity was restored to 45% after turning them off. The excellent low-temperature catalytic activity is mainly due to the amorphous phase, pore structure and high specific areas.

Preparation and operating conditions for cobalt cerium oxide catalysts used in the conversion of synthesis gas into light olefins

Cobalt cerium oxides, prepared using a co-precipitation procedure, were studied as catalysts for the conversion of synthesis gas to light olefins (C2-C4). Specifically, we studied the effect of a range of preparation variables, including the molar ratio of the [Co]/[Ce] of the precipitation solution, ageing time and calcination temperature. In addition, the effects of supports and promoters on the catalysts’ activity and selectivity and a range of reaction temperatures using synthesis gas with different H2/CO molar feed ratios were investigated. The catalyst containing a molar ratio of 80% Co and 20% Ce, aged for 2 h, supported with 15 wt% SiO2 without any promoter, at an operating temperature of 450 °C and an H2/CO feed ratio of 2/1 (GHSV = 4500 h−1), performed optimally for the conversion of synthesis gas to light olefins. The characterization of both the precursors and the calcined catalysts by powder X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller specific surface area measurements and thermal analysis methods, including TGA and DSC, show that all the preparation variables influenced the catalyst precursor structure.